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Biomedical subjects

Z Kiss

Publications and source records attributed to Z Kiss.

At least 109 records · Page 6Linked to original sources
PubMed1988

Phorbol ester stimulates the synthesis of sphingomyelin in NIH 3T3 cells. A diminished response in cells transformed with human A-raf carrying retrovirus.

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated the synthesis of sphingomyelin (CerPCho) from a [14C]choline-labelled phosphatidylcholine (PtdCho) pool in NIH 3T3 cells. Maximal stimulation (68%) of CerPCho synthesis, accompanied by an increase (38%) in its cellular content, required only 2 nM TPA. Higher concentrations of TPA (2-100 nM) had progressively less effect on CerPCho synthesis which correlated with increased hydrolysis of precursor PtdCho. In cells transformed with human or mouse A-raf carrying retroviruses TPA-stimulated PtdCho hydrolysis, but not CerPCho synthesis, suggesting independent regulation of these processes by the TPA-stimulated signal transduction system.

Animals↗
PubMed1988

Effect of parathion and methylparathion on protein content of chicken embryo muscle in vivo.

Chicken eggs were treated with 0.4 per cent solutions of parathion or methylparathion for four or eight days, and the two-dimensional gel electrophoretic protein pattern of cervical muscles of eighteen days old embryos was analyzed. Both compounds significantly decreased the content of alpha-actinin, alpha-tubulin and beta-tubulin after four days treatment, and, in addition, that of three other related proteins (gamma-proteins) after eight days treatment. Under in vitro phosphorylating conditions, both methylparathion and parathion specifically inhibited the phosphorylation of one isoform of beta-tubulin. Data suggest that the muscle-damaging effects of organophosphorous insecticides, such as parathion and its derivates, may be related to the decrease of tissue content of certain cytoskeletal proteins.

Animals↗
PubMed1988

Phorbol ester stimulation of sphingomyelin synthesis in human leukemic HL60 cells.

Pulse-chase experiments, performed with 14C-labeled choline, were used to study the possible effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the terminal step of sphingomyelin (CerPCho) synthesis from phosphatidylcholine in intact human promyelocytic leukemic HL60 cells. Addition of TPA for the chase period significantly increased the rate of CerPCho synthesis; maximal stimulation (104%) required only 3 nM TPA. Treatment of cells with TPA for 6 h also increased the mass of CerPCho by 35%. Sphingosine (25 microM) or H7 (100 microM), inhibitors of protein kinase C (PKC) in vitro, inhibited some, but not all effects of TPA on endogenous protein phosphorylation in intact cells, and failed to inhibit TPA-stimulated synthesis of CerPCho. However, bryostatin, mezerein, 1-oleoyl-2-acetylglycerol, and polymyxin B, previously all shown to stimulate PKC in vivo, also stimulated the synthesis of CerPCho. It is suggested that the effect of phorbol ester on CerPCho synthesis is mediated by a subtype of PKC which responds to known activators of enzyme but is not inhibited by H7 or sphingosine.

Bryostatins↗
PubMed1988

Cooperative interactions of protein kinase C and cAMP-dependent protein kinase systems in human promyelocytic leukemia HL60 cells.

Interactions of protein kinase C (PKC) and cAMP-dependent protein kinase (PKA) systems were investigated in HL60 cells. It was found that the differentiating effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) were potentiated by dibutyryl cAMP (dbcAMP) or prostaglandin E2 (PGE2). In addition, dbcAMP or PGE2 inhibited TPA-induced binding of PKC to plasma membrane, leading to decreased protein phosphorylation, and promoted subsequent redistribution of enzyme to the nuclear membrane region. The findings are consistent with the hypothesis that PKC and PKA systems regulate cooperatively the phenotypical differentiation of leukemic cells.

Biological Transport↗
PubMed1988

Temporal changes in intracellular distribution of protein kinase C during differentiation of human leukemia HL60 cells induced by phorbol ester.

Immunocytochemical methods were used to study protein kinase C (PKC) distribution in HL60 cells during the entire course of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced differentiation. After an initial translocation of PKC from cytoplasm to plasma membrane, the enzyme was localized close to the nuclear membrane region at day 1 of TPA treatment. PKC was associated with nuclei at day 2 and with nuclei, cytoplasma and plasma membrane at days 3 and 5. Attachment of cells to substratum (day 2) was accompanied by increased phosphorylation of several nuclear proteins. At day 7, the differentiated cells became detached and PKC in these cells was largely cytoplasmic. In view of the crucial role of PKC in cell differentiation, it is expected that changes in its intracellular localization have physiological significance.

Cell Differentiation↗
PubMed1988

Vanadate stimulated NADH oxidation in sarcoplasmic reticulum membrane.

Vanadate stimulated NADH oxidation was detected in sarcoplasmic reticulum membrane preparations. The reaction showed enzymatic character, with half maximal activating concentration of 1.2 mM vanadate and maximal NADH oxidation 50 nmol/mg protein/minute. Acidic pH, micromolar free Ca2+ concentration and decavanadate addition increased the rate of NADH oxidation. The described enzyme activity is similar to the ones observed in erythrocyte liver and cardiac plasma membranes. The vanadate stimulated NADH oxidation in sarcoplasmic reticulum preparations does not seem to originate from other contaminating membrane elements. The presence of this enzyme activity in the sarcoplasmic reticulum should be taken into consideration when planning experiments with vanadate, especially when measuring ATPase activity through NADH oxidation with coupled enzymatic assay.

Animals↗
PubMed1988

Falsely high high-density lipoprotein triglyceride values by the heparin-manganese precipitation method.

Recent evidence indicates that high-density lipoprotein triglyceride (HDL-Tg) may be a predictor of coronary artery disease. We examined three methods for HDL-Tg measurement, comparing results obtained by measurement of Tg in the supernate after heparin-manganese chloride (heparin-Mn) precipitation of EDTA-treated plasma (I) with results obtained after preparative ultracentrifugation (II and III). In II, we used heparin-Mn precipitation of low-density lipoprotein (LDL) from the infranate after ultracentrifugation at d 1.006 to remove very-low-density lipoprotein (VLDL). In III, we performed sequential flotation ultracentrifugation at d 1.006 and 1.063, then measured Tg in the d greater than 1.063 fraction. Method I gave significantly higher HDL-Tg results than II and III, which gave essentially identical results. The difference in results between I and II was not caused by the presence of heparin or manganese chloride, because these were used in both methods. Prior removal of VLDL in II and III resulted in lower HDL-Tg values, and subsequent removal of LDL by precipitation or ultracentrifugation did not alter final HDL-Tg values. The higher values obtained in I were the result of the presence of VLDL-rich unsedimented precipitate in the supernate.

Chemical Precipitation↗
PubMed1987

Phorbol ester inhibits phosphatidylserine synthesis in human promyelocytic leukaemia HL60 cells. Possible involvement of free radicals and correlation with phosphorylation of nuclear protein 1b.

Treatment of human promyelocytic leukaemia HL60 cells in conditioned medium with 12-O-tetradecanoylphorbol 13-acetate (TPA) for 4 h resulted in 25-30% inhibition of labelling of phosphatidylserine (PS) with [U-14C]serine. PS labelling was 40% lower, and no inhibitory TPA effect was observed when the experiments were performed in fresh medium. Cycloheximide or puromycin also inhibited PS labelling by 38-44%; their inhibitory effects were non-additive with that of TPA and occurred only in conditioned medium. Catalase (CAT) and superoxide dismutase (SOD), both free-radical scavengers, and H7, a protein kinase C inhibitor, reversed to various extents the inhibitory effect of TPA on PS synthesis. On the other hand, chlorobenzoic acid, a free-radical-generating agent, also inhibited PS synthesis by 22% after 4 h treatment when conditioned medium was used. When ethanolamine was added to cells in conditioned medium to quench PS formation through the exchange of free serine with the ethanolamine moiety of phosphatidylethanolamine (PE), PS labelling was decreased by 33% and the inhibitory TPA effect was significantly decreased. On the other hand, ethanolamine had marginal quenching effect on PS labelling when added to cells in fresh medium. TPA increased the phosphorylation of various proteins in the cells, including protein lb (Mr 80,000; pI 5.5) shown to be localized mainly in the nuclear fraction. Chlorobenzoic acid selectively stimulated the phosphorylation of protein lb, whereas CAT and SOD specifically attenuated the TPA-stimulated phosphorylation of this protein. All these agents affected phosphorylation of protein lb only if conditioned medium was used. The findings suggested that net synthesis of PS through the base-exchange mechanism was stimulated in HL60 cells by cell products present in the conditioned medium. TPA inhibited this stimulated PS synthesis by a mechanism which appeared to involve active oxygen species and protein synthesis and might be related to the phosphorylation of protein lb.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1987

Immunocytochemical localization of protein kinase C in resting and activated human neutrophils.

An immunocytochemical method was used to determine possible changes in the subcellular distribution of protein kinase C (PKC) in human neutrophils in response to opsonized latex beads and zymosan. While in resting cells most of the PKC immunoreactivity was localized in the cytoplasm, a redistribution of PKC to the plasma and phagosomal membranes was observed in cells treated with latex beads or zymosan for 5-20 min, suggesting a participation of PKC in endocytosis.

Adult↗
PubMed1987

Comparative effects of polymyxin B, phorbol ester and bryostatin on protein phosphorylation, protein kinase C translocation, phospholipid metabolism and differentiation of HL60 cells.

The effects of protein kinase C (PKC) inhibitor polymyxin B (PMB) and PKC activators 12-O-tetradecanoylphorbol-13-acetate (TPA) and bryostatin on intact HL60 cells were examined. It was found that each of the three agents exhibited similar effects on phosphorylation of certain endogenous proteins, PKC translocation from cytoplasm to plasma membrane and formation of CDP-choline. TPA, however, was the only agent that stimulated phosphatidylcholine formation. Differentiation of HL60 cells was potently induced by TPA; in comparison bryostatin was a relatively weaker inducer and PMB was without effect. The data indicated that the effects of the PKC inhibitor PMB on intact cells could not be predicted by its in vitro activity, and that certain TPA-dependent but PKC-independent reactions might be crucial in HL60 cell differentiation.

Bryostatins↗
PubMed1987

Cyclic AMP-like effects of polyamines on phosphatidylcholine synthesis and protein phosphorylation in human promyelocytic leukemia HL60 cells. Comparison with the effects of phorbol ester.

Spermine or putrescine increased cAMP levels through a catalase-sensitive mechanism, resulting in, most notably, a dephosphorylation of protein A (Mr 45,000, pI 5.15) and protein B (Mr 45,000, pI 4.9) and slightly increased phosphatidylcholine (PC) synthesis in HL60 cells. Exogenous dibutyryl cAMP mimicked the polyamine effects. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) also promoted the protein dephosphorylation and PC synthesis, the effects augmented by R59022 and mimicked by exogenous 1-oleoyl-2-acetylglycerol. The effects of spermine (or dibutyryl cAMP) and TPA on PC synthesis were synergistic. It was suggested that cAMP-dependent protein kinase and protein kinase C might mediate, in an independent but inter-related manner, the effects of polyamines and TPA.

Bucladesine↗
PubMed1987

Differential effects of various protein kinase C activators on protein phosphorylation in human acute myeloblastic leukemia cell line KG-1 and its phorbol ester-resistant subline KG-1a.

Human myeloid leukemia KG-1 cells are induced to differentiate to macrophage-like cells by tumor-promoting phorbol esters, such as 12-O-tetradecanoylphorbol-13-acetate (TPA). Cells from the cloned subline, KG-1a, unlike the parental line, are resistant to the differentiating effect of TPA. In the present studies, we investigated in these cells protein phosphorylation stimulated by various protein kinase C activators, including 1-oleoyl-2-acetylglycerol in the presence of the diacylglycerol kinase inhibitor R59022, TPA, mezerein, and bryostatin. All the agents stimulated, to a greater extent and with a higher potency, phosphorylation of several proteins in KG-1 cells than in KG-1a cells. On the other hand, these agents markedly stimulated phosphorylation of other proteins in KG-1a cells compared to that in KG-1 cells. The findings indicated that the actions of the diacylglycerol, 1-oleoyl-2-acetylglycerol, and the non-metabolizable activators (TPA, mezerein, and bryostatin) were very similar but not fully equivalent; and that KG-1a cells exhibited altered (increased or decreased) phosphorylation patterns, perhaps related to the TPA resistance characteristic of this subline of cells.

Bryostatins↗
PubMed1987

Antileukemic agent alkyllysophospholipid regulates phosphorylation of distinct proteins in HL60 and K562 cells and differentiation of HL60 cells promoted by phorbol ester.

The tumor-promoting 12-0-tetradecanoylphorbol-13-acetate (TPA) stimulated phosphorylation of several proteins in block I (including protein Ia) and protein 3 in HL60 cells. The antileukemic agent alkyllysophospholipid (ALP) inhibited the TPA-stimulated phosphorylation of these proteins and the TPA-induced differentiation of the cells. In comparison, TPA only stimulated phosphorylation of protein 3 in K562 cells which, in contrast, were not induced to differentiate by TPA and lacked protein Ia and had a very high basal phosphorylation of protein B. ALP inhibited phosphorylation of protein 3 as well as protein B in K562 cells. The data suggest that the presence of distinct phosphoproteins and regulation of their phosphorylation may be related to the selective susceptibility of the two leukemia cell lines to the maturating effect of TPA and cytotoxicity of ALP.

Antineoplastic Agents↗